This invention relates to a system for aiding a user in aiming a receiving antenna at a satellite from which radio signals are to be received.
The use of orbiting satellites in relaying signals from one ground station to one or more other ground stations has become commonplace in a variety of situations including telephone signal transmission, video or television signal transmission, data transmission, etc. In more recent years, satellites have become an important part of communication systems in which information from a single originating station is relayed via a satellite to multiple receiving stations. The information may be available for all receiving stations, or it may be encoded to identify particular receiving stations which are to recognize and have access to the information. The receiving stations would include processors capable of processing received information to determine if a respective receiving station was to have access to the transmitted information.
In setting up a satellite communication system, it is necessary that each receiving station locate and aim the receiving antenna toward the satellite from which the signals are to be received. Because of the distance of travel of the signals and the usual limited size of receiving antennae or dishes, it is necessary to be very precise in aiming a receiving antenna at the satellite in question. If this is not done precisely, then the received signal may be too weak to enable the accurate recovery of information therefrom.
In video satellite transmission systems, it is common to use a television set and a so-called "squawker" to adjust and aim the antenna at the satellite in question. A "squawker" is a device which may be carried to the roof or other location of a receiving antenna, connected to the antenna, and then operated in conjunction with positioning of the antenna to determine which position yields the strongest signal from the satellite. This approach works well in video satellite systems since the video signals relayed by the satellites in orbit are many in number and easily identified by simply viewing the received television picture to determine if it is the desired program.
In satellite audio/data communication networks, there is usually no video signal to aid in locating the correct signal. There are many satellites in geostationary orbit (the satellites appear to be stationary but are in fact orbiting the earth at the same rate that the earth rotates) and these satellites all relay or transmit similar signals. Thus, the use of a "squawker" is generally ineffective since there is no way to distinguish one satellite from another.
It is typical in satellite audio/data communication to identify a particular signal from a satellite by observing the profile of the received signal on a spectrum analyzer. The installer compares the representation of the received signals on the screen of the spectrum analyzer with that of the desired signal and moves the dish until the correct satellite is located. The installer may then fine-adjust the dish antenna to maximize the strength of the received signal. These spectrum analyzers, as might be expected, are bulky, complicated to use, and expensive.